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Local and Large-Scale Environment of Seyfert Galaxies
We present a three-dimensional study of the local (<=100h-1 kpc) and the large-scale (<=1 h-1 Mpc)environment of the two main types of Seyfert AGN galaxies. For thispurpose we use 48 Seyfert 1 galaxies (with redshifts in the range0.007<=z<=0.036) and 56 Seyfert 2 galaxies (with0.004<=z<=0.020), located at high galactic latitudes, as well astwo control samples of nonactive galaxies having the same morphological,redshift, and diameter size distributions as the corresponding Seyfertsamples. Using the Center for Astrophysics (CfA2) and Southern SkyRedshift Survey (SSRS) galaxy catalogs (mB~15.5) and our ownspectroscopic observations (mB~18.5), we find that within aprojected distance of 100 h-1 kpc and a radial velocityseparation of δv<~600 km s-1 around each of ourAGNs, the fraction of Seyfert 2 galaxies with a close neighbor issignificantly higher than that of their control (especially within 75h-1 kpc) and Seyfert 1 galaxy samples, confirming a previoustwo-dimensional analysis of Dultzin-Hacyan et al. We also find that thelarge-scale environment around the two types of Seyfert galaxies doesnot vary with respect to their control sample galaxies. However, theSeyfert 2 and control galaxy samples do differ significantly whencompared to the corresponding Seyfert 1 samples. Since the maindifference between these samples is their morphological typedistribution, we argue that the large-scale environmental differencecannot be attributed to differences in nuclear activity but rather totheir different type of host galaxies.
| The First INTEGRAL AGN Catalog
We present the first INTEGRAL AGN catalog, based on observationsperformed from launch of the mission in 2002 October until 2004 January.The catalog includes 42 AGNs, of which 10 are Seyfert 1, 17 are Seyfert2, and 9 are intermediate Seyfert 1.5. The fraction of blazars is rathersmall, with five detected objects, and only one galaxy cluster and nostarburst galaxies have been detected so far. A complete subset consistsof 32 AGNs with a significance limit of 7 σ in the INTEGRAL ISGRI20-40 keV data. Although the sample is not flux limited, thedistribution of sources shows a ratio of obscured to unobscured AGNs of1.5-2.0, consistent with luminosity-dependent unified models for AGNs.Only four Compton-thick AGNs are found in the sample. Based on theINTEGRAL data presented here, the Seyfert 2 spectra are slightly harder(Γ=1.95+/-0.01) than Seyfert 1.5 (Γ=2.10+/-0.02) and Seyfert1 (Γ=2.11+/-0.05).
| Correlations among multiwavelength luminosities of star-forming galaxies
It has been known for two decades that a tight correlation existsbetween global far-infrared (FIR) and radio continuum (1.4 and 4.8 GHz)fluxes/luminosities from star-forming galaxies, which may be explainedby formation activities of massive stars in these galaxies. For thisvery reason, a correlation might also exist between X-ray and FIR/radioglobal luminosities of galaxies. We analyse data from the ROSAT All-SkySurvey and from IRAS to show that such correlation does indeed existbetween FIR (42.5-122.5μm) and soft X-ray (0.1-2.4 keV) luminositiesLX and LFIR in 17 normal star-forming galaxies(NSFGs), including 16 late-type galaxies and one host-dominant Seyfertgalaxy, as well as in 14 active star-forming galaxies (ASFGs) consistingof starburst-dominant Seyfert galaxies. The quantitative difference insuch correlations in NSFGs and in ASFGs may be interpreted in terms ofevolutionary variations from classic starburst galaxies tostarburst-dominant Seyfert galaxies. Meanwhile, some low-luminosityactive galactic nuclei (LLAGNs) tend to exhibit such a correlation thatwe infer for star-forming galaxies, implying that star-formingactivities might be more dominant in LLAGNs. In contrast, AGN-dominantSeyfert galaxies do not show such a LX versus LFIRcorrelation; this is most likely related to accretions towardssupermassive black holes (SMBHs) in galactic nuclei. In order toestablish a physical connection between theLX-LFIR correlation and global star formation rate(SFR) in galaxies, we empirically derive bothLX-LB and LFIR-LB relationswith the blue-band luminosity LB roughly representing themass of a galaxy. It appears that the more massive galaxies are, themore star formation regions exist in these galaxies. The global SFR isnot only associated with the mass of a galaxy but also closely relatedto the level of star-forming activities therein. We propose a relationbetween soft X-ray luminosity and SFR in star-forming galaxies. In orderto probe the LX-LFIR relation, we construct anempirical model in which both FIR and X-ray emissions consist of twocomponents with one being closely associated with star formation and theother one not. Based on this model, we infer a linear relation betweenFIR/soft X-ray in star formation regions and radio luminosities, and geta linear relation between LX and LFIR forstar-forming regions.
| Stellar populations and dust extinction in non-active and Seyfert spiral galaxies
Metallicity and age gradients of the stellar populations and dustextinction are studied for a sample of 32 non-active, seven type 1Seyfert (S1) and 17 type 2 Seyfert (S2) spiral galaxies. The samplegalaxies cover the whole range from face-on to edge-on view, and thevariation of the optical and near-infrared colour gradients in the discas a function of the inclination angle is investigated in order toseparate colour changes caused by population gradients from those due todust effects.The measurements show that the observed colour gradients in the discs ofthe non-active galaxies are significantly larger than those found forthe S1 and S2 galaxies. In the near-infrared wavelengths, however, thesedifferences disappear, and the colour gradients are the same for allthree galaxy types. No systematic differences are found between thecolour gradients of the discs of the S1 galaxies and those of the S2galaxies.The data are compared to model images of dusty galaxies with a varietyof age and metallicity gradients in the disc. The radial variations ofthe optical and near-infrared colours of the model galaxies arecalculated from the radial changes of the ages and the metallicities ofthe stars, using broad-band colours of a single stellar population. Thestellar content at a given position in the disc is determined by theaverage age, the metallicity and the star formation history.For the non-active galaxies, the observed colour gradients arerepresented best by a model with a metallicity gradient, with the innerregions of the stellar disc being more metal-rich than the outerregions. However, the presence of an age gradient, with the innerregions of the stellar disc being older than the outer regions, cannotbe ruled out. For the S1 and S2 galaxies, the comparison between dataand models indicates that the age and metallicity gradients in thestellar disc are small. As far as the internal dust extinction isconcerned, the comparison between data and models indicates that boththe non-active and the S2 galaxies show significant dust extinction, butthey are not optically thick.
| The Tully-Fisher Relation for Hickson Compact Groups
We investigate the properties of the B-band Tully-Fisher (TF) relationfor 25 compact group galaxies, using Vmax derived from 2-Dvelocity maps. Our main result is that the majority of the HicksonCompact Group (HCG) galaxies lie on the TF relation, although with largescatter. However, 20% of the galaxies, including the lowest-masssystems, seem to have higher B luminosities, for a given mass, oralternatively, a mass which is too low for their luminosities. We favourthe scenario of brightening of the outliers due to either enhanced starformation or merging, rather than truncation of the dark halo due tointeractions, to explain the position of the outliers on the TFrelation.
| A Complete Sample of Soft X-Ray-Selected AGNs. I. The Data
We present the optical spectra and simple statistical analysis for acomplete sample of 110 soft X-ray-selected AGNs. About half of thesources are narrow-line Seyfert 1 galaxies (NLS1's), which have thesteepest X-ray spectra, the strongest Fe II emission, and slightlyweaker [O III] λ5007 emission than broad-line Seyfert 1's(BLS1's). Kolmogorov-Smirnov tests show that NLS1's and BLS1's haveclearly different distributions of the X-ray spectral slopeαX, X-ray short-term variability, and Fe II equivalentwidths and luminosity and Fe II/Hβ ratios. The differences in the[O III]/Hβ and [O III] equivalent widths are only marginal. Wefound no significant differences between NLS1's and BLS1's in theirrest-frame 0.2-2.0 X-ray luminosities, rest-frame 5100 monochromaticluminosities, bolometric luminosities, redshifts, and their Hβequivalent widths.Based in part on observations at the European Southern Observatory, LaSilla (Chile), with the 2.2 m telescope of the Max Planck Society duringMPI and ESO time, and the ESO 1.52 m telescope during ESO time in 1995September and 1999 September.
| Timescales of Soft X-Ray Variability and Physical Constraints in Active Galactic Nuclei
We present soft X-ray variability timescales for 65 active galacticnuclei (AGNs) derived from ROSAT Position Sensitive Proportional Counterpointing data. For these 65 objects with obvious exponential increasingor decreasing patterns in their light curves, we use the exponentialtimescales and find they are more suitable for analyzing ROSATlight-curve data. We also discuss some physical constraints on thecentral engine implied by our results. Assuming that this soft X-rayvariability exponential timescale is approximately equal to the thermaltimescale of the standard accretion disk, we obtain the accretion rate,the size of the soft X-ray radiation region, and the compactnessparameter for 37 AGNs, using their recently estimated central black holemasses. For 12 of these 37 AGNs, the radii of the gravitationalinstability in the standard thin accretion disks are obtained using thecentral black hole masses and the calculated accretion rates. These areconsistent with the results from the reverberation mapping method. Theseresults provide supporting evidence that such gravitationalinstabilities contribute to the formation of the broad-line regions inAGNs.
| Dynamical Effects of Interactions and the Tully-Fisher Relation for Hickson Compact Groups
We investigate the properties of the B-band Tully-Fisher (T-F) relationfor 25 compact group galaxies, using Vmax derived fromtwo-dimensional velocity maps. Our main result is that the majority ofthe Hickson Compact Group galaxies lie on the T-F relation. However,about 20% of the galaxies, including the lowest-mass systems, havehigher B luminosities for a given mass, or alternatively, a mass that istoo low for their luminosities. We favor a scenario in which outliershave been brightened because of either enhanced star formation ormerging. Alternatively, the T-F outliers may have undergone truncationof their dark halo due to interactions. It is possible that in somecases both effects contribute. The fact that the B-band T-F relation issimilar for compact group and field galaxies tells us that thesegalaxies show common mass-to-size relations and that the halos ofcompact group galaxies have not been significantly stripped insideR25. We find that 75% of the compact group galaxies studied(22 out of 29) have highly peculiar velocity fields. Nevertheless, acareful choice of inclination, position angle, and center, obtained fromthe velocity field, and an average of the velocities over a large sectorof the galaxy enabled the determination of fairly well-behaved rotationcurves for the galaxies. However, two of the compact group galaxies HCG91a and HCG 96a, which are the most massive members in M51-like pairs,have very asymmetric rotation curves, with one arm rising and the otherone falling, indicating most probably a recent perturbation by the smallclose companions.
| The Seyfert Population in the Local Universe
The magnitude-limited catalog of the Southern Sky Redshift Survey(SSRS2) is used to characterize the properties of galaxies hostingactive galactic nuclei (AGNs). Using emission-line ratios, we identify atotal of 162 (3%) Seyfert galaxies out of the parent sample with 5399galaxies. The sample contains 121 Seyfert 2 galaxies and 41 Seyfert 1galaxies. The SSRS2 Seyfert galaxies are predominantly in spirals oftypes Sb and earlier or in galaxies with perturbed appearance as theresult of strong interactions or mergers. Seyfert galaxies in thissample are twice as common in barred hosts as the non-Seyfert galaxies.By assigning galaxies to groups using a percolation algorithm, we findthat the Seyfert galaxies in the SSRS2 are more likely to be found inbinary systems when compared with galaxies in the SSRS2 parent sample.However, there is no statistically significant difference between theSeyfert and SSRS2 parent sample when systems with more than two galaxiesare considered. The analysis of the present sample suggests that thereis a stronger correlation between the presence of the AGN phenomenonwith internal properties of galaxies (morphology, presence of bar,luminosity) than with environmental effects (local galaxy density, groupvelocity dispersion, nearest neighbor distance).Partly based on observations at European Southern Observatory (ESO),under the ESO-ON agreement to operate the 1.52 m telescope.
| Nature and environment of Very Luminous Galaxies
The most luminous galaxies in the blue passband have a largercorrelation amplitude than L* galaxies. They do not appear tobe preferentially located in rich clusters or groups, but a significantfraction of them seem to be in systems which include fainter members. Wepresent an analysis of fields centered on 18 Very Luminous Galaxies(MB <=-21) selected from the Southern Sky Redshift Survey2, based on new observations and public data of the 2dF Galaxy RedshiftSurvey; we present also additional data on a CfA VLG and on Arp 127. Wefind that all the selected VLGs are physically associated with faintercompanions. Moreover, there is a relation between the VLG morphology(early or late) and the dynamical properties of the system, whichreflects the morphology-density relation. 6 out of the 18 SSRS2 VLGs areearly type galaxies: 2 are in the center of rich Abell clusters withvelocity dispersion sigma ~ 600 km s-1, and the other 4are in poor clusters or groups with sigma ~ 300. The VLG extractedfrom the CfA catalog is also an elliptical in a Zwicky cluster. Theremaining 2/3 of the sample are late-type VLGs, generally found inpoorer systems with a larger spread in velocity dispersion, from ~ 100up to ~ 750 km s-1. The low velocity dispersion, late-typeVLG dominated systems appear to be analogous to our own Local Group. Thepossibile association of VLG systems with dark matter halos with masscomparable to rich groups or clusters, as suggested by the comparablecorrelation amplitude, would imply significant differences in the galaxyformation process. This work also shows that observing fields aroundVLGs represents an effective way of identifying galaxy systems which arenot selected through other traditional techniques.Figures 1, 2 and Appendix B are only available in electronic form athttp://www.edpsciences.org
| Gas kinematics of a sample of five Hickson Compact Groups. The data
We present Fabry Perot observations of galaxies in five Hickson CompactGroups: HCG 10, HCG 19, HCG 87, HCG 91 and HCG 96. We observed a totalof 15 galaxies and we have detected ionized gas for 13 of them. We wereable to derive 2D velocity, monochromatic, continuum maps and rotationcurves for the 13 objects. Almost all galaxies in this study arelate-type systems; only HCG 19a is an elliptical galaxy. We can see atrend of kinematic evolution within a group and among different groups -from strongly interacting systems to galaxies with no signs ofinteraction - HCG 10 exhibits at least one galaxy strongly disturbed;HCG 19 seems to be quite evolved; HCG 87 does not show any sign ofmerging but a possible gas exchange between two galaxies; HCG 91 couldbe accreting a new intruder; HCG 96 exhibits past and presentinteractions.Based on observations collected at the European Southern Observatory, LaSilla, Chile and at the Canada-France-Hawaii Observatory, Hawaii, USA.Tables 1 and 2, Figs. 1, 3, 5, 7, 9, 11, 13, 15, 23 are only availablein electronic form at http://www.edpsciences.org
| Seyfert Galaxies with Circumnuclear/Nuclear Starbursts
In this paper, we present our preliminary results on Seyfert galaxieswith circumnuclear/nuclear starburst (SB) activity. We have searched therecent available literature and found 76 active galaxies with clearevidence of nuclear SB activity, among which 16 are Seyfert 1s, 51Seyfert 2s, and 9 LINERs. After studying the 51 Seyfert 2s, we find thatthose Seyfert 2s with hidden Seyfert 1 nuclei, have similarInfrared-Radio properties as Seyfert 1 galaxies, and are different from``real'' Seyfert 2s without a hidden Seyfert 1 nucleus. The later aresimilar to starburst galaxies.
| X-ray luminosities of galaxies in groups
We have derived the X-ray luminosities of a sample of galaxies ingroups, making careful allowance for contaminating intragroup emission.The LX:LB and LX:LFIRrelations of spiral galaxies in groups appear to be indistinguishablefrom those in other environments, however the elliptical galaxies fallinto two distinct classes. The first class is central-dominant groupgalaxies, which are very X-ray luminous and may be the focus of groupcooling flows. All other early-type galaxies in groups belong to thesecond class, which populates an almost constant band ofLX/LB over the range9.8
| A study of neutral hydrogen in five small galaxy groups
High-resolution Hi imaging observations of a heterogeneous sample ofsmall galaxy groups are presented. The five galaxy groups studied show abroad range of individual Hi properties: e.g. loose groups surroundingLGG 138 and the genuinely compact LGG 455 are identified; a massive ringof neutral gas is discovered encircling two luminous galaxies in the LGG138 group; a galaxy-sized mass of Hi is found in LGG 455 confined to anextragalactic cloud which exceeds the threshold density for starformation, yet is optically invisible; and the CCG 1 group is argued tobe a chance alignment of Centaurus cluster galaxies. Global results ofthe study are that the deficit of Hi flux in synthesis imaging datacompared with single-dish data is put forward as a quantitative measureof the diffuseness of neutral gas in galaxy groups; several groupscontain gas-poor galaxies that ordinarily would contain detectablequantities of Hi - this is interpreted as being caused by an increasedchance of gas-sweeping collisions in the group environment; and someevidence is found to support previous findings that compact groupspreferentially occur in loose systems.
| Disc scalelengths of non-active and active spiral galaxies
Disc scalelengths rD are determined for a sample of 32non-active and 28 active spiral galaxies from optical CCD images. For 21of the 32 non-active galaxies and 20 of the 28 active galaxies B, V, Rand I data have been obtained, while for the remaining galaxies only Band I images have been taken. For 18 of the 21 non-active galaxies,which are measured in all four passbands, rD decreasessystematically from B to I, whereas such a decrease is found for onlyfour of the 20 active galaxies with BVRI data. For the non-activegalaxies, the ratios rD(B)/rD(I),rD(V)/rD(I) and rD(R)/rD(I)increase systematically with increasing apparent ellipticity ɛof the galaxies. For the active galaxies, no systematic variation of anyof the ratios with increasing ɛ is found. The variation ofrD(B)/rD(I) with ɛ is compared with modelcalculations. For the non-active galaxies, the data are represented bestby a model with a stellar disc that has an intrinsic colour gradient andwith a central optical depth in the B band for face-on view ofτ0B=3. For the active galaxies, the best agreement between data andmodels is found for models with a stellar disc with no intrinsic colourgradient and no dust. The best-fitting model for the non-active galaxiesdoes not reproduce the data of the active galaxies. The main conclusionof this work is that structural differences seem to exist between thediscs of non-active and active galaxies. The non-active galaxies showsignificant colour gradients within their discs, whereas the activegalaxies do not. These gradients are probably caused by a combination ofan intrinsic colour gradient within the stellar disc, and dustextinction. Furthermore, the measurements indicate that the non-activegalaxies show significant dust extinction in the centre, but they areoptically thin in the outer regions. The active galaxies do not seem tohave intrinsic colour gradients within the stellar disc and they areoptically thin throughout the disc.
| ROSAT-HRI observations of six southern galaxy pairs
We present the detailed analysis of the X-ray data for 6 pairs, isolatedor in poor groups, observed at high resolution with the ROSAT HRI . Inall cases, the stronger X-ray source is associated with the brighterearly-type member and is extended. The extent varies from galactic togroup scale, from 3 (RR 210b) to 182 kpc( RR 22a). The fainter membersare detected only in two pairs, RR 210 and RR 259. Except for one case,no significant substructures have been detected in the X-ray maps,possibly also as a consequence of the poor statistics. The core radii ofthe X-ray surface brightness profiles are in the range 1-3 kpc. Thedistribution of the luminosities of galaxies in pairs encompasses a verywide range of both luminosities and LX / LBratios, in spite of the very small number of objects studied so far. Ourdata provide no evidence that pair membership affects the X-rayproperties of galaxies. Observation are discussed in the context of thepair/group evolution.
| Global molecular gas properties of Seyfert galaxies II. Analysis of the results
We use the data published in Paper I and \cite{ca99} to determine theglobal molecular gas luminosities and distributions in a sample of 22Seyfert galaxies. From this we find definite differences in the CO toHCN luminosity ratios between the near-by and distant galaxies of thesample. This is perhaps due to a selection effect where we only observethe brightest of the distant sources. With regard to distributions, wefind in the near-by (mapped) sample that the CO is usually much widerdistributed than the central telescope beam and that the HCN isconsiderably more extended beyond the ~ 1 kpc often cited in theliterature. In fact this molecule has been detected as far as ~5 kpcfrom the centre of NGC 1365. We may also have detected a bar in HCN inNGC 5033. Also, using the data to complement the results of\cite{cur99p}, we find (LCO)/(LFIR)(Sy2)~(LCO)/(LFIR)(Sy1) i.e. no difference in themolecular gas luminosities between the two main Seyfert classes. In factwe consider it more meaningful to discuss the differences between thenear-by and distant sample (irrespective of Seyfert type), although bothof these samples may show evidence that much of the far infraredluminosity could arise from an active galactic nucleus as opposed tobeing predominantly due to vigorous star formation. We do believe,however, that improved statistics would be of little value indistinguishing between these two scenarios and that future highresolution observations are the key to resolving this issue. Based onresults collected at the European Southern Observatory, La Silla, Chileand Onsala Space Observatory, Sweden.
| X-ray variability in a complete sample of Soft X-ray selected AGN
We present ROSAT All-Sky Survey and ROSAT pointed observations (PSPC andHRI) of a complete sample of 113 bright soft X-ray AGN selected from theROSAT Bright Source Catalog. We compare these observations in order tosearch for extreme cases of flux and spectral X-ray variability - X-raytransient AGN. Three definite transients and one transient candidate arefound. The other sources show amplitude variations typically by factorsof 2-3 on timescales of years. We found that the variability strength ontimescales of days is a function of the steepness of the X-ray spectrum:steeper X-ray objects show stronger variability than flat X-ray spectrumsources. We also present new HRI measurements of our extreme X-raytransients IC 3599 and WPVS007. We discuss possible models to explainthe X-ray transience and the variabilities observed in the non-transientsources. Based in part on observations at the European SouthernObservatory La Silla (Chile) with the 2.2~m telescope of theMax-Planck-Society during MPG and ESO time and the ESO 1.52~m telescope.
| Relationship between Infrared and Radio Emission of Seyfert Galaxies
The relationships between the monochromatic luminosity of Seyfertgalaxies at frequencies of 0.408, 1.49, and 4.85 GHz and the integratedluminosity in the far infrared (IR) range are investigated. At all radiofrequencies they are linear and equally close. Some Seyfert galaxies, ofmorphological types S0/a, E, and S0, have a far higher radio luminositythan Seyfert spiral galaxies with the same IR luminosity. Most of themare found to have compact central radio components. Seyfert spiralgalaxies follow the same relationship between radio and IR emission asnon-Seyfert spiral galaxies. The relationships between radio and IRluminosity for the individual groups of galaxies of spectral types Sy1-Sy 1.5 and Sy 1.8-Sy 2 are also linear.
| Narrow-band Emission-Line and Continuum Images of Seyfert Galaxies
We present narrow-band emission line (Hα + [N II] λλ6548, 6583, [O III] λλ 4959, 5007) as well as green or redcontinuum images of selected Seyfert galaxies. The sample includes NGC7214, IC 4218, Akn 479, Mrk 915, IC 1515 and F 348.
| The ROSAT Bright Survey: II. Catalogue of all high-galactic latitude RASS sources with PSPC countrate CR > 0.2 s-1
We present a summary of an identification program of the more than 2000X-ray sources detected during the ROSAT All-Sky Survey (Voges et al.1999) at high galactic latitude, |b| > 30degr , with countrate above0.2 s-1. This program, termed the ROSAT Bright Survey RBS, isto more than 99.5% complete. A sub-sample of 931 sources with countrateabove 0.2 s-1 in the hard spectral band between 0.5 and 2.0keV is to 100% identified. The total survey area comprises 20391deg2 at a flux limit of 2.4 x 10-12 ergcm-2 s-1 in the 0.5 - 2.0 keV band. About 1500sources of the complete sample could be identified by correlating theRBS with SIMBAD and the NED. The remaining ~ 500 sources were identifiedby low-resolution optical spectroscopy and CCD imaging utilizingtelescopes at La Silla, Calar Alto, Zelenchukskaya and Mauna Kea. Apartfrom completely untouched sources, catalogued clusters and galaxieswithout published redshift as well as catalogued galaxies with unusualhigh X-ray luminosity were included in the spectroscopic identificationprogram. Details of the observations with an on-line presentation of thefinding charts and the optical spectra will be published separately.Here we summarize our identifications in a table which contains opticaland X-ray information for each source. As a result we present the mostmassive complete sample of X-ray selected AGNs with a total of 669members and a well populated X-ray selected sample of 302 clusters ofgalaxies with redshifts up to 0.70. Three fields studied by us remainwithout optical counterpart (RBS0378, RBS1223, RBS1556). While the firstis a possible X-ray transient, the two latter are isolated neutron starcandidates (Motch et al. 1999, Schwope et al. 1999).
| The ROSAT/IRAS Galaxy Sample Revisited
Galaxies in the ROSAT/IRAS sample were selected by their soft X-ray(0.1-2.4 keV) and far-infrared (lambda = 60 μm) emission. Therelatively large uncertainties in the original ROSAT and IRAS positionscaused some contamination by close pairs and forced the exclusion ofmost ``high-flux'' (S > 10 Jy at lambda = 100 μm) IRAS sourcesfrom the original sample. We used new 1.4 GHz VLA images of all objectsnorth of delta = -45 deg along with improved X-ray and far-infraredpositions to eliminate incorrect identifications, many of which appearedto be starburst galaxies with high X-ray luminosities, log [X(ergs^-1)]> 43. We also used VLA images to search for new X-ray identificationsamong the ``high-flux'' sources with delta > -45 deg. Only two werefound, indicating that luminous starburst galaxies have relatively lowsoft X-ray luminosities, in part due to absorption by a denseinterstellar medium. No starburst galaxies in our revised sample haveX-ray luminosities approaching log [X(ergs^-1)] = 43. We conclude thatmost galaxies in the revised ROSAT/IRAS sample contain X-ray-emittingactive galactic nuclei (AGNs) residing in star-forming disks that emitmost of the lambda = 60 μm radiation. Normal and starburst galaxiesprobably do not account for a significant fraction of the soft X-raybackground.
| The Southern Sky Redshift Survey
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
| Properties of Very Luminous Galaxies
Recent analysis of the data from the Southern Sky Redshift Surveyextension (SSRS2) based on cell counts and the two-point correlationfunction has shown that very luminous galaxies are much more stronglyclustered than fainter galaxies. In fact, the amplitude of thecorrelation function of very luminous galaxies (L > L^*)asymptotically approaches that of R >= 0 clusters. In this paper weinvestigate the properties of the most luminous galaxies, with blueabsolute magnitudes M_B <= -21. We find that (1) the population mixis comparable to that in other ranges of absolute magnitude; (2) only asmall fraction are located in bona fide clusters; (3) the brightgalaxy-cluster cross-correlation function is significantly higher onlarge scales than that measured for fainter galaxies; (4) thecorrelation length of galaxies brighter than M_B ~ -20.0, expressed as afunction of the mean interparticle distance, appears to follow theuniversal dimensionless correlation function found for clusters andradio galaxies; (5) a large fraction of the bright galaxies are ininteracting pairs, while others show evidence for tidal distortions andsome appear to be surrounded by faint satellite galaxies. We concludethat very luminous optical galaxies differ from the normal population ofgalaxies in both clustering and other respects. We speculate that thispopulation is a highly biased tracer of mass, being associated with darkhalos with masses more comparable to clusters than to typical loosegroups.
| Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
| ROSAT All-Sky Survey observations of IRAS galaxies. I. Soft X-ray and far-infrared properties
The 120 000 X-ray sources detected in the RASS II processing of theROSAT All-Sky Survey are correlated with the 14 315 IRAS galaxiesselected from the IRAS Point Source Catalogue: 372 IRAS galaxies showX-ray emission within a distance of 100 arcsec from the infraredposition. By inspecting the structure of the X-ray emission in overlayson optical images we quantify the likelihood that the X-rays originatefrom the IRAS galaxy. For 197 objects the soft X-ray emission is verylikely associated with the IRAS galaxy. Their soft X-ray properties aredetermined and compared with their far-infrared emission. X-ray contourplots overlaid on Palomar Digitized Sky Survey images are given for eachof the 372 potential identifications. All images and tables displayedhere are also available in electronic form.
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| A catalogue of spatially resolved kinematics of galaxies: Bibliography
We present a catalogue of galaxies for which spatially resolved data ontheir internal kinematics have been published; there is no a priorirestriction regarding their morphological type. The catalogue lists thereferences to the articles where the data are published, as well as acoded description of these data: observed emission or absorption lines,velocity or velocity dispersion, radial profile or 2D field, positionangle. Tables 1, 2, and 3 are proposed in electronic form only, and areavailable from the CDS, via anonymous ftp to cdsarc.u-strasbg.fr (to130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| Identification of soft high galactic latitude RASS X-ray sources. I. A complete count-rate limited sample
We present a summary of spectroscopic identifications for a completesample of bright soft high galactic latitude X-ray sources drawn fromthe ROSAT All-Sky Survey which have PSPC count-rates CR > 0.5 {ctss}(-1) and hardness ratios HR1 < 0. Of a total of 397 sources, 270had catalogued counterparts although most of these were not previouslyknown as X-ray sources; of the remaining 127 sources neither X-ray noroptical properties were previously known. Of the whole sample of verysoft X-ray sources 155 were also discovered by the Wide-Field-Camera onboard ROSAT. We present spectroscopic identifications of 108 sources andother identifications for further 18 sources; 1 source remainsunidentified so far. In practically all cases a unique opticalcounterpart exists facilitating identification. The largest sourceclasses are AGN, magnetic cataclysmic variables, and hot white dwarfs.Based in part on observations with the ESO/MPI 2.2m telescope at LaSilla, Chile
| Spectroscopy of the circumnuclear emission line regions in Seyfert galaxies. II. NGC 7214
This paper is the second of a series (Radovich and Rafanelli\cite{rad:raf}) devoted to the investigation of the emission lineproperties of the circumnuclear and extranuclear regions in a sample ofnearby Seyfert galaxies. Our aim is to identify star formation regionsaround the active nucleus and to derive their properties like starformation rate and dust content, and compare them with those observed innon-active galaxies. We show that photoionization models may fit theobserved line ratios both in the nuclear and circumnuclear regions ofthe Sy 1.2 galaxy NGC 7214. In the nucleus, components with differentdensities must be considered. In the circumnuclear regions, line ratiosto projected distances of ~ 2 kpc from the nucleus are typical ofionization by a power law. At higher distances ( ~ 5-8 kpc) they arefitted either by a thermal continuum or assuming that both stars and thenon thermal source contribute to the ionization of the gas. A simpleinterpretation is suggested, in the framework of the unified model forSeyfert galaxies. Evidence for enhanced star formation, maybe related tothe ongoing interaction with a close spiral galaxy, is found in only oneregion. Based on observations collected at ESO - La Silla (Chile)
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